DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 23 Feb 2018, 13:18

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 14 posts ]  Go to page 1, 2  Next
Author Message
PostPosted: 08 Jul 2009, 14:12 
Offline
Project Author
User avatar

Joined: 14 Oct 2008, 17:35
Posts: 901
Location: Dartmouth, Nova Scotia
Not even a day ago, I was at a friends house, and her dad wanted to show me this stereo he found on the curb. It was in the garage, he hooked up speakers and we powered it up... all the lights came on but it was obviouse that something was horribly wrong. First of all two of the input switches were obviously not triggering properly (AM and AUX stayed pushed in and lit) and secondly I found there to be a strange heat and odour coming out of the chassis, no smoke just a smelly burnt odour. There was no audio ither, no his no noise, nothing at all.

So in the end I got a free-bee! yay another broken or partially broken stereo to add to the ever growing collection, and not only that but this one happens to be a golden boat ancor with one blown up channel!!! :bawling:

But wait.... this time is different, I have the full user manual and schematic! :sing: And unlike the LXI amplifier I can completely bipass the preamp stage until I fix the switches, too bad it wasn't just the switches.

I will post pictures of the redisection soon and the unfindable SCHEMATIC, but for now I am in the search of 2SA1076/2SC2526 substitute replacements here: http://www.diyaudio.com/forums/showthre ... adid=37265

_________________
My Mini 12AU7 Tube Preamp, Pioneer SX-D7000, JVC XL-V221BK, JBL L80T, DCM TF700


Top
 Profile  
 
PostPosted: 08 Jul 2009, 16:14 
Offline
Project Author
User avatar

Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
I always liked the blue displays on the older Pioneers. The 2SA1076 crossed over to an NTE93 PnP HiFi power Audio amp http://www.nteinc.com/specs/10to99/pdf/nte92.pdf The specs look very close to the specs in your other link. The second transistor did not cross but if they are complementary in the same circuit I am sure it is the NTE92. Just check the specs a little further.
Some of the older amps will have a pungent almost hot and sour smell if the owners smoked. 20~30 years of nicotine can rest in the circuitry and get rather funky.


Top
 Profile  
 
PostPosted: 08 Jul 2009, 16:29 
Offline
Project Author
User avatar

Joined: 14 Oct 2008, 17:35
Posts: 901
Location: Dartmouth, Nova Scotia
Thanks roggom, the NTE units actually have the same package as the originals, but how would they compare to some of the other subs like the ONsemi?

_________________
My Mini 12AU7 Tube Preamp, Pioneer SX-D7000, JVC XL-V221BK, JBL L80T, DCM TF700


Top
 Profile  
 
PostPosted: 08 Jul 2009, 17:27 
Offline
Project Author
User avatar

Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
Well, many techs/ repair guys scoff at the NTE because in many cases they are too generic. I have used them in Marantz rebuilds and have had great success. Just match the voltage, current and Hfe and then make sure to calibrate the idle current. I have not used onsemi so I can not compare. This is also a good opportunity for a recap project of the main amp board.

Rogers


Top
 Profile  
 
PostPosted: 08 Jul 2009, 21:41 
Offline
Project Author
User avatar

Joined: 14 Oct 2008, 17:35
Posts: 901
Location: Dartmouth, Nova Scotia
Well I guess I will go for it then, the store I order parts from sells me NTE products all the time, I just bought an LA4270 chip but is the NTE version. :up:

I will be replacing allot of numorus components on the main board, 3 very crispy resistors and two small TO-92 transistors I found missing their tops, and the drivers may be blown as well, so this could be a major rebuild, but one thing is for sure someone tried to fix other parts of the receiver as well because of some obvious not original parts in the tuner PS.

I have taken lots of pictures and have yet to draw up my version of the schematic, but thanks for the help. :up:

_________________
My Mini 12AU7 Tube Preamp, Pioneer SX-D7000, JVC XL-V221BK, JBL L80T, DCM TF700


Top
 Profile  
 
PostPosted: 08 Jul 2009, 22:04 
Offline
Project Author
User avatar

Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
Not sure if I have suggested this in past threads, but I really suggest making a "poor mans variac" this allows you to troubleshoot and if the short is still in the circuit the lamp will go on, instead of frying the output transistors. Variacs are good but some do not have current protection. You can make one with a power strip and a small desk lamp around 40watt bulb. Just put the lamp in series with the hot wire.

Hopefully you can find the root of the problem as those amps are really stylish.


Top
 Profile  
 
PostPosted: 09 Jul 2009, 18:26 
Offline
Project Author
User avatar

Joined: 14 Oct 2008, 17:35
Posts: 901
Location: Dartmouth, Nova Scotia
Actually, I have a pair of 12V 2-3A regulated power supplies that I could use to test the amplifier at a lower voltage where I can monitor for shorts and at least make sure that there is audio coming out. Because this is of much lower power I can easily use the light bulb technique to make sure that there are no shorts, and like I said, things don't seem to blaow up as fast. ;)

I guess all I have to really take into account is how to rebias the amplifier to work at this voltage, which gives me the idea that I could attempt class "A" bias, but there would be an insane amount of heat, and would definetly need larger PS. :down:

I am gathering a parts list so I am far away from testing this beast.

_________________
My Mini 12AU7 Tube Preamp, Pioneer SX-D7000, JVC XL-V221BK, JBL L80T, DCM TF700


Top
 Profile  
 
PostPosted: 21 Jul 2009, 10:41 
Offline
Project Author
User avatar

Joined: 14 Oct 2008, 17:35
Posts: 901
Location: Dartmouth, Nova Scotia
I guess I have to put this project in a box for a while.... The matched NTE's are going to cost me 200 dollars!!!! :hot: :( :bawling:

Is this amplifier really worth the money? I really want to get it working but I have too many other projects to spend that kind of money, unless there are cheaper substitutes but those NTE's are beasts and I don't even know how blown up the main board is yet but was thinking that for now I could get cheaper outputs just to make sure the amplifier works, like cheap TIP36/35's, have piles of them.

I suppose I could just get four NTE's to get the blown up channel working since the transistors on the other channel don"t have shorts and test good on my anologue meter at 10-12 ohms? :confused:

_________________
My Mini 12AU7 Tube Preamp, Pioneer SX-D7000, JVC XL-V221BK, JBL L80T, DCM TF700


Top
 Profile  
 
PostPosted: 21 Jul 2009, 12:17 
Offline
Project Author
User avatar

Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
Looks like mouser has them for $40 http://www.mouser.com/Search/ProductDet ... L8CxfuM%3d, still, that is quite a bit of money for trannies. I would put a request on audio karma or something for a parts unit. If you are lucky you can find another with a working channel and more spare parts.

Rogers


Top
 Profile  
 
PostPosted: 21 Jul 2009, 22:10 
Offline
Project Author
User avatar

Joined: 14 Oct 2008, 17:35
Posts: 901
Location: Dartmouth, Nova Scotia
I guess that would be a good idea if I didn't all ready have enough broken equipment parts as it is, but I'm not out of ideas yet.

I think I may all ready know the answer to this question, but will ask it any ways, is it ok to mix different brands of transistors at the output? The store I went to had all whole lot of cross references to those NTE's, some were beefy Sankens and there were RCA and ONsemi I think, is it ok to use these others even if the NPN's and PNP's are different brands? :xfingers:

_________________
My Mini 12AU7 Tube Preamp, Pioneer SX-D7000, JVC XL-V221BK, JBL L80T, DCM TF700


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 14 posts ]  Go to page 1, 2  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 9 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy